Zinc alloyed iron pyrite ternary nanocrystals for band gap broadening

Iron pyrite (FeS2) is one of the most promising photovoltaic materials with high natural abundance and low cost but with a lower-than-optimum band gap of 0.95 eV. Here the feasibility of band gap broadening was explored by zinc alloying of FeS2 nanocrystals (NCs). A significant amount of zinc up to 6 at%, 30 times higher than previously reported, was incorporated into the FeS2 NCs. In contrast to band gap bowing predicted by first-principles calculations, a band gap enlargement of ∼0.1 eV was observed by zinc alloying. A more than five-times reduction of dark current in the zinc alloyed FeS2 photoconductor was observed and should ascribe to the increased band gap.